A bifunctional earphone set

Abstract: In construction of an earphone set incorporating a vibratory membrane accompanied with a ceramic wafer, a coactive magnetic electroacoustic conversion is arranged facing the vibratory membrane in a manner such that the vibratory membrane reproduces human voices on receipt of corresponding electric acoustic signals whereas the conversion unit issues electric acoustic signals on collection of corresponding human voices at the vibratory membrane.

Description: Background of the invention The present invention relates to a bifunctional earphone set comprising a housing provided with an ear socket to be inserted into the ear canal of an user, a vibratory membrane arranged within the housing in a position substantially perpendicular to a longitudinal axis of the ear socket, and a piezoelectric ceramic wafer arranged within the housing facing the vibratory membrane and connected to a signal output terminal. In the following paragraphs, two special terms will be used in relation to the mode of dialogue between two persons. The first one is "concurrent dialogue" and the second one is "alternate dialogue". First, the concurrent dialogue. In the case of this mode, one person can intercept a story by the other person and stories by the two persons can overlap. This mode of dialogue is quite suited for emergent conversation in rescue or battle operations in which quick communication is highly wanted by two persons. Next the alternate dialogue. In the case of this mode, one person cannot intercept a story by the other person and stories by the two persons cannot overlap. Once the second person starts his (or her) story, the first person must wait until a story by the second person terminates. There is an indispensable waiting interval in conversation. Even when one person highly wants to communicate some abrupt information during a story by the other person, he (or she) cannot do so as long as the other person continues his (or her) story. Clearly, this mode of dialogue is very inconvenient in the case of emergent conversation in which many pieces of unexpected information have to cross. Generally in the field of electroacoustic treatment of human voices, voices are collected directly from a human mouth using an electric pickup such as a microphone. In the case of this voice collection system, however, the microphone is liable to pick up unnecessary ambient sounds in addition to human voices to be collected and mixing of such ambient sounds causes generation of harsh noises in voice reproduction. In order to cut off such ambient sounds, it was proposed by the inventor in his earlier Japanese application Hei. 3-240194 to collect human voices through vibrations of the tympanic membrane of a speaker at generation of voices. That is, vibrations of the tympanic membrane are sensed by a compact ear set provided with a built-in pickup such as a microphone. Collection of voices within the ear of the speaker only well excludes mixing of ambient sounds. In the case of this prior invention, the compact ear set functions as a microphone. However, a separate receiver has to be prepared for reception and electroacoustic conversion of transmitted electric signals which carry acoustic information. Usually, collection of human voices within an ear is classified into two systems. One is air conduction system and the other is called bone conduction system. As well known, the interior of an ear is surrounded by several, contiguous bones. When a voice is generated by a user, the voice causes corresponding vibrations of these bones. In the case of the bone conduction system, such vibrations of the bones is collected by a sensor arranged near the bones. It is said in the field of art, however, that the bone conduction system is much lower in its sensitivity than the air conduction system. It is noted that the present invention is based on the air conduction system. Generally, electroacoustic conversion is classified into two conversion modes. That is, the first one is voice-to-signal conversion generally carried out by a microphone and the second one is signal-to-voice conversion generally carried out by a receiver. Some bifunctional devices have already been proposed in the field of art in order to carry out both of the two conversions by use of only one single unit. An earphone set proposed in US-A-3′995′113 is one example of such a bifunctional device. The device includes a hollow housing provided with an ear socket to be inserted into the ear canal of a user. A vibratory membrane is arranged in an air chamber defined by the housing and a piezoelectric element is mechanically connected to the vibratory membrane. The piezoelectric element is connected to an electric terminal adapted for reception and issue of electric signals. In the voice-to-signal conversion mode, voice is introduced into the air chamber through the ear socket and sonic pressure generated thereby causes vibration of the vibratory membrane. This vibration urges the piezoelectric element to issue corresponding electric signals to the electric terminal. In the signal-to-voice conversion mode, electric signals are applied to the piezoelectric element via the electric terminal and the piezoelectric element urges the vibratory membrane to vibrate. The air chamber resonates for generation of corresponding voices. Thus, the piezoelectric element is required to work in both conversion modes but unable to operate in both conversion modes at one time. So, although the device of this earlier proposal allows alternate dialogue, it is quite unsuited for the above-described concurrent dialogue. In FR-A-2′559′984 is disclosed a bifunctional earphone set of a different kind, which is designed to avoid use of a vibratory membrane as a microphone. The microphone portion of the set is formed by a cylindrical piezoelectric unit extending along the ear socket to sense vocal vibration conducted by the user's skull, that is to say that the user's voice is collected by the above described bone conduction system. The receiving or earphone portion is physically separate from the microphone portion and comprises a membrane driven by an electromagnetic or piezoelectric conversion unit. A transistorized switching means can be provided for automatic shutting off of the microphone when the receiver is in operation, such that alternate dialogue is possible but not concurrent dialogue. Summary of the invention It is thus the primary object of the present invention to provide a compact earphone set which functions as a microphone as well as a receiver, such that it can be quite suited for concurrent dialogue. A bifunctional earphone set in accordance with a first aspect of the present invention is defined in claim 1. A bifunctional earphone set in accordance with a second aspect of the present invention is defined in claim 3. Brief description of the drawings Fig. 1 is a side view, partly in section, of the first embodiment of the earphone set in accordance with the present invention, Fig. 2 is a side view, partly in section, of the second embodiment of the earphone set in accordance with the present invention, Fig. 3 is a perspective view of the earphone set incorporating the present invention, and Fig. 4 is a block diagram of an electroacoustic system using the earphone set of the present invention. Description of the preferred embodiments The first embodiment of the earphone set in accordance with the present invention is shown in Fig. 1 in which the above-described magnetic electroacoustic conversion unit includes one set of coil only. More specifically in Fig. 1, an earphone set 1 includes a small, pan-shaped housing 10 made up of a main body 11 and an ear socket 12 projecting from one planar end of the main body 11. One or more air holes 13 are formed through the wall of the main body 11 in order to prevent undesirable resonance of human voices introduced into the main body 11 through the ear socket 12. Support brackets 14 are arranged within the main body 11 near the ear socket 12 in order to hole the piezoelectric vibration unit 20 whilst allowing free vibration of the latter. At least one air hole 15 is formed through each support bracket 14 again for prevention of human voice resonance. The piezoelectric vibration unit 20 includes a vibratory membrane 21 held by the support bracket 14 at a position facing the ear socket 12 of the housing 10. A ceramic wafer 22 is bonded to the vibratory membrane 21 on a side facing the ear socket 12. This ceramic wafer 21 is sandwiched by a pair of conductor films 23 which form different poles of the ceramic wafer 22. The conductor films 23 are accompanied with leads 24, respectively, which are bundled together to form a cord 25. As shown in Fig. 3, the cord 25 extends outside the housing 10 for connection to a terminal 26. A magnetic, electroacoustic conversion unit 30 is arranged facing the vibratory membrane 21 of the vibration unit 20 at a position remote from the ear socket 12. The electroacoustic conversion unit 30 includes a permanent magnet 31 and an iron core 32 arranged within the magnetic field of the permanent magnet 31 and a coil 33 is wound about the iron core 32. The coil 33 is accompanied with leads 34 which are bundled together to form a cord 35. As shown in Fig. 3, the cord 35 extends outside the housing 10 for connection to a terminal 36. The earphone set of the above-described construction operates in two fashions as follows. First, the earphone set 1 operates as a microphone, when human voices are introduced into the housing 10 via the air socket 12, the vibratory membrane 21 of the vibration unit 20 is driven for corresponding vibrations which apply pressure to the ceramic wafer 22. Depending on change in intensity of the applied pressure, the ceramic wafer 22 generates electric acoustic signals of correspondingly varying voltages. The electric acoustic signals are then transmitted to a proper outside sound system via the cord 25 and the terminal 26. Next, the earphone set 1 operates as a receiver. In this case, electric acoustic signals are transmitted to the conversion unit 30 from a proper outside system via the terminal 36 and the cord 35. On receipt of the electric acoustic signals, the coil 33 varies magnetic fluxed in the iron core 32 to cause corresponding change in the magnetic field. Depending on the change in the magnetic field, the vibratory membrane 21 of the vibration unit 20 vibrates at frequencies corresponding to change in the magnetic field to generate voices corresponding to the electric acoustic signals received at the conversion unit 30. The second embodiment of the earphone set in accordance with the present invention is shown in Fig. 2 in which the magnetic electroacoustic conversion unit includes two sets of coils. In this case, the constructions of the housing 10 and the piezoelectric vibration unit 20 are substantially same as those in the first embodiment. Like the first embodiment, a magnetic, electroacoustic conversion unit 40 is arranged facing the vibratory membrane 21 of the vibration unit 20 at position remote from the ear socket 12. The electroacoustic conversion unit 40 includes a permanent magnet 41 and an iron core 42 arranged within the magnetic field of the permanent magnet 41 and a pair of coils 43 and 44 are coaxially wound about the iron core 42. The first coil 43 is accompanied with leads 45 which are bundled together to form a cord such as the cord 25 used in the first embodiment. This coil 43 is used for receiver application. The second coil 44 is accompanied with leads 46 which are bundled together to form a cord such as the cord 35 used in the first embodiment. This coil 44 is used for microphone application. The earphone set of the above-described construction operates in two fashions as follows. First, the earphone set 1 operates as a microphone. When human voices are introduced into the housing 10 via the air socket 12, the vibratory membrane 21 of the vibration unit 20 is driven for corresponding vibrations. This vibration causes corresponding variation in the magnetic fluxes in the iron core 42. In accordance with this variation in magnetic fluxes, the second coil 44 generates corresponding electric acoustic signals which are in turn transmitted to a proper outside sound system via the leads 46. Next, the earphone set 1 operates as receiver. In this case, electric acoustic signals are transmitted to the conversion unit 40 from a proper outside system via the leads 45. On receipt of the electric acoustic signals, the first coil 43 varies magnetic fluxes in the iron core 42 to cause corresponding change in the magnetic field. Depending on the change in the magnetic field, the vibratory membrane 21 of the vibration unit 20 vibrates at frequencies corresponding change in the magnetic field to generate voices corresponding to the electric acoustic signals received at the conversion unit 40. In actual use of the earphone set 1 in accordance with the present invention, proper amplifiers 50 may be inserted into the electric circuit as shown in Fig. 4. It should be noted that sound-signal conversion is generally based on two different systems, i.e. a dynamic drive system and a magnetic drive system, both using a combination of a coil with a magnet. The present invention is based on the magnetic drive system. In the case of the dynamic drive system, a coil formed in one body with a vibratory membrane (or plate) is driven for reciprocal movement on the magnet. Movement of the coil can be designed relatively large. Stated otherwise, a small signal input can produce a large sound output. However, this system requires high precision in winding of the coil, inevitably resulting in high production cost despite its large sound output. In the case of the magnetic drive system, a vibratory membrane (or plate) is driven for reciprocal movement but a coil remains stationary on the magnet. The system cannot convert a small signal input to a large sound output although it does not require high precision in coil winding and, as a consequence, its production cost is much lower than the dynamic drive system. However, because the earphone is located within the ear of the user and quite close to the user's tympanic membrane, no large sound output is required in actual use. The present invention well utilized this special background. The earphone set in accordance with the present invention is bifunctional. Stated otherwise, two different circuits, i.e. a microphone circuit and a receiver circuit, are contained in a single set and possible interference between the different functional circuit may incur a problem of howling in sound generation. Such a trouble may be easily overcome by incorporating a proper IC circuit into the construction of the earphone set. In accordance with the present invention, a single earphone set can be used as a microphone as well as a receiver. It should be additionally appreciated that, in the system of the present invention, only one vibratory membrane operates in two ways, i.e. sound input for signal output and signal input for sound output. This is the very characteristic and advantageous feature of the present invention. It should be appreciated that the present invention employs a function sharing system in its electroacoustic conversion. This function sharing system is the heart of the present invention which enables the concurrent dialogue stated above. In the voice-to-signal conversion mode, the ceramic wafer 22 plays the main role. That is, on receipt of human voice, the vibratory membrane 21 vibrates to apply pressure to the ceramic wafer 22 attached thereto and the ceramic wafer 22 generates an electric signal to be passed to the output terminal. Here, the coil 33 stays out of this operation at all. In the signal-to-voice conversion mode, the coil 33 plays the main role. That is, on receipt of electric signals at the input terminal, the coil 33 varies its magnetic field and the vibratory membrane 21 vibrates to generate a voice. Here, the ceramic wafer 22 stays out of this operation at all. Thus, in terms of electric operation, the ceramic wafer 22 is involved in the voice-to-signal conversion only whereas the coil 33 is involved in the signal-to-voice conversion only, although the vibratory membrane 21 is mechanically involved in both of the operations. Stated otherwise, the ceramic wafer 22 and the coil 33 can operate concurrently thanks to the operation sharing system. The voice-to-signal conversion and the signal-to-voice conversion are compatible at the same time and such compatibility allows the above-described concurrent dialogue special to the present invention.

Claims: A bifunctional earphone set comprising a housing (11) provided with an ear socket (12) to be inserted into the ear canal of an user, a vibratory membrane (21) arranged within the housing (11) in a position substantially perpendicular to a longitudinal axis of the ear socket (12), and a piezoelectric ceramic wafer (22) arranged within the housing (11) facing the vibratory membrane and connected to a signal output terminal, characterized in that the ceramic wafer (22) is attached directly to a first planar side of the vibratory membrane (21), that a magnetic electroacoustic conversion unit (30) is arranged within the housing (11) facing the second planar side of the vibratory membrane (21) and, that the electroacoustic conversion unit (30) includes at least one electromagnetic coil (33) connected to a signal input terminal, whereby the vibratory membrane (21) reproduces human voice on receipt of corresponding electric acoustic signals at the signal input terminal and the ceramic wafer (22) issues electric acoustic signals to the signal output terminal on collection of corresponding human voice at the vibratory membrane (21). A bifunctional earphone set as claimed in claim 1, wherein said ceramic wafer (22) is connected to an outside sound generating system via first conductive leads (24), and said magnetic electroacoustic conversion unit (30) includes a permanent magnet (31), an iron core (32) coupled to said permanent magnet, and said coil (33) mounted to said iron core and connected to an outside electric signal reception system via second conductive leads (34). A bifunctional earphone set comprising a housing (11) provided with an ear socket (12) to be inserted into the ear canal of a user, a vibratory membrane (21) arranged within the housing (11) in a position substantially perpendicular to a longitudinal axis of the ear socket (12) and a piezoelectric ceramic wafer (22) arranged within the housing (11) facing the vibratory membrane (2), characterized in that the ceramic wafer (22) is attached to a first planar side of the vibratory membrane (21), that a magnetic electroacoustic conversion unit (30) is arranged within the housing (11) facing the second planar side of the vibratory membrane (21) whilst including first and second coils (43, 44) coaxially spaced along said longitudinal axis, that the first coil (43) is arranged close to the vibratory membrane (21) and connected to a signal input terminal, and that the second coil (44) is arranged remote from the vibratory membrane (21) and connected to a signal output terminal, whereby, on receipt of electric acoustic signals at the signal input terminal, the vibratory membrane (21) reacts to changes in the magnetic flux generated by the first coil (43) for reproduction of corresponding human voices and, on collection of human voices at the vibratory membrane (21), the second coil (44) issues corresponding electric acoustic signals to the signal output terminal.

Inventors: KIMURA HIROFUMI C O SOEI ELECT, KIMURA, HIROFUMI, C/O SOEI ELECTRIC CO., LTD.
Applicants: SOEI ELECTRIC CO LTD, SOEI ELECTRIC CO., LTD.
Application year: 1994
Main classification: H04R1
IPC codes: H04M1, H04R1, H04R17